In the fluid handling art, it is common practice to conduct fluids through fluid passages, such as ducts, tubing and pipes, under variable and/or constant head pressures. The head pressures determine the rate and volume of flow of the liquids through the passages.
In many instances, the rate and volume of flow through and issuing from the passages must be very accurately controlled. In such situations, any variations of the head pressures alter the rate and volume of flow. To prevent variations in the rate and volume of flow of liquids through passages in response to variations of the head pressures thereon, the art provides various kinds and/or forms of flow metering devices that are most commonly in the nature of valves and orifice plates or fittings; most of which are well known to those skilled in the art.
Those flow control devices provided by the prior art that are accurate, tend to be quite complicated and costly to make and maintain. The simpler and less costly prior art flow control devices tend to be somewhat inaccurate, though considerably more practical to use and maintain and far less costly.
One of the more accurate and yet most practical forms of flow control devices provided by the prior art are elastic orifice plates with upstream and downstream surfaces and that are arranged to extend across their related flow passages. Those elastic orifice plates are formed so that fluid pressure at their upstream surfaces (independent of the pressure differentials thereacross) cause the plates to deform in a manner to constrict or reduce the effective cross-sectional area of the orifices therein. The extent to which the orifices are constricted is proportional to increases of pressure (upstream of the plates) that are above a neutral pressure at which the plates commence to function to meter the fluid flowing through them.
The effective range of pressure that the above-noted elastic orifice plates can effectively meter the fluids flowing through them is rather limited. Accordingly, various "sizes" of those devices are provided for handling different fluids at different pressures and in different volumes. Accordingly, when elastic orifice plates are used, one selects that available size of plate that most closely meets his requirements. Accordingly, in a great number of instances, a user of those plates cannot find a size of plate that exactly meets his needs and is left to adopt and use that available size of plate that most closely meets his needs. In doing so, he must often compromise that which he seeks to achieve.
Elastic orifice plates of the character referred to above are non-adjustable and, to the best of my knowledge and belief, the art has failed to provide any means which effectively enables adjustment of the flow rate of liquids through them.